eqn - format equations for troff
eqn [ -rvCNR ] [ -dxy ]
[ -Tname ] [ -Mdir ]
[ -fF ] [ -sn ]
[ -pn ] [ -mn ]
[ files... ]
It is possible to have whitespace between a command line option
and its parameter.
This manual page describes the GNU version of eqn, which is part of the
groff document formatting system. eqn compiles descriptions of
equations embedded within troff input files into commands that are
understood by troff. Normally, it should be invoked using the -e
option of groff. The syntax is quite compatible with Unix eqn. The
output of GNU eqn cannot be processed with Unix troff; it must be
processed with GNU troff. If no files are given on the command line, the
standard input will be read. A filename of - will cause the standard
input to be read.
eqn searches for the file eqnrc in the directories
given with the -M option first, then in /usr/share/tmac,
/usr/share/tmac, and finally in the standard macro directory
/usr/share/tmac. If it exists, eqn will process it before the
other input files. The -R option prevents this.
GNU eqn does not provide the functionality of neqn: it does
not support low-resolution, typewriter-like devices (although it may work
adequately for very simple input).
- -dxy
- Specify delimiters x and y for the left and right
end, respectively, of in-line equations. Any delim statements in
the source file overrides this.
- -C
- Recognize .EQ and .EN even when followed by a character
other than space or newline.
- -N
- Don't allow newlines within delimiters. This option allows eqn to
recover better from missing closing delimiters.
- -v
- Print the version number.
- -r
- Only one size reduction.
- -mn
- The minimum point-size is n. eqn will not reduce the
size of subscripts or superscripts to a smaller size
than n.
- -Tname
- The output is for device name. The only effect of this is to define
a macro name with a value of 1. Typically
eqnrc will use this to provide definitions appropriate for the
output device. The default output device is ps.
- -Mdir
- Search dir for eqnrc before the default directories.
- -R
- Don't load eqnrc.
- -fF
- This is equivalent to a gfont F command.
- -sn
- This is equivalent to a gsize n command. This option
is deprecated. eqn will normally set equations at whatever the
current point size is when the equation is encountered.
- -pn
- This says that subscripts and superscripts should be
n points smaller than the surrounding text. This option is
deprecated. Normally eqn makes sets subscripts and superscripts at
70% of the size of the surrounding text.
Only the differences between GNU eqn and Unix eqn are described here.
Most of the new features of GNU eqn are based on TeX. There
are some references to the differences between TeX and GNU eqn below;
these may safely be ignored if you do not know TeX.
eqn gives each component of an equation a type, and adjusts the spacing
between components using that type. Possible types are:
- ordinary
- an ordinary character such as `1' or `x';
- operator
- a large operator such as `Σ';
- binary
- a binary operator such as `+';
- relation
- a relation such as `=';
- opening
- a opening bracket such as `(';
- closing
- a closing bracket such as `)';
- punctuation
- a punctuation character such as `,';
- inner
- a subformula contained within brackets;
- suppress
- spacing that suppresses automatic spacing adjustment.
Components of an equation get a type in one of two ways.
- type t e
- This yields an equation component that contains e but that
has type t, where t is one of the types mentioned
above. For example, times is defined as
- The name of the type doesn't have to be quoted, but quoting protects from
macro expansion.
- chartype t text
- Unquoted groups of characters are split up into individual characters, and
the type of each character is looked up; this changes the type that is
stored for each character; it says that the characters in text from
now on have type t. For example,
- chartype "punctuation" .,;:
- would make the characters `.,;:' have type punctuation whenever they
subsequently appeared in an equation. The type t can also be
letter or digit; in these cases chartype changes the
font type of the characters. See the Fonts subsection.
- e1 smallover e2
- This is similar to over; smallover reduces the size of
e1 and e2; it also puts less vertical space between
e1 or e2 and the fraction bar. The over primitive
corresponds to the TeX \over primitive in display styles;
smallover corresponds to \over in non-display styles.
- vcenter e
- This vertically centers e about the math axis. The math axis is the
vertical position about which characters such as `+' and `−' are
centered; also it is the vertical position used for the bar of fractions.
For example, sum is defined as
- { type "operator" vcenter size +5 \(*S }
- e1 accent e2
- This sets e2 as an accent over e1. e2 is assumed to
be at the correct height for a lowercase letter; e2 will be moved
down according if e1 is taller or shorter than a lowercase letter.
For example, hat is defined as
- dotdot, dot, tilde, vec, and dyad are
also defined using the accent primitive.
- e1 uaccent e2
- This sets e2 as an accent under e1. e2 is assumed to
be at the correct height for a character without a descender; e2
will be moved down if e1 has a descender. utilde is
pre-defined using uaccent as a tilde accent below the
baseline.
- split "text"
- This has the same effect as simply
- but text is not subject to macro expansion because it is quoted;
text will be split up and the spacing between individual characters
will be adjusted.
- nosplit text
- This has the same effect as
- but because text is not quoted it will be subject to macro
expansion; text will not be split up and the spacing between
individual characters will not be adjusted.
- e opprime
- This is a variant of prime that acts as an operator
on e. It produces a different result from prime in a
case such as A opprime sub 1: with
opprime the 1 will be tucked under the prime as a
subscript to the A (as is conventional in mathematical
typesetting), whereas with prime the 1 will be a
subscript to the prime character. The precedence of opprime is the
same as that of bar and under, which is higher than that of
everything except accent and uaccent. In unquoted text
a ' that is not the first character will be treated like
opprime.
- special text e
- This constructs a new object from e using a troff(1)
macro named text. When the macro is called, the string 0s
will contain the output for e, and the number registers
0w, 0h, 0d, 0skern, and 0skew will
contain the width, height, depth, subscript kern, and skew
of e. (The subscript kern of an object says how much
a subscript on that object should be tucked in; the skew of an
object says how far to the right of the center of the object an accent
over the object should be placed.) The macro must modify 0s so that
it will output the desired result with its origin at the current point,
and increase the current horizontal position by the width of the object.
The number registers must also be modified so that they correspond to the
result.
- For example, suppose you wanted a construct that `cancels' an expression
by drawing a diagonal line through it.
-
.EQ
define cancel 'special Ca'
.EN
.de Ca
. ds 0s \
\Z'\\*(0s'\
\v'\\n(0du'\
\D'l \\n(0wu -\\n(0hu-\\n(0du'\
\v'\\n(0hu'
..
- Then you could cancel an expression e with
cancel { e }
- Here's a more complicated construct that draws a box round an
expression:
- .EQ
define box 'special Bx'
.EN
.de Bx
. ds 0s \
\Z'\h'1n'\\*(0s'\
\Z'\
\v'\\n(0du+1n'\
\D'l \\n(0wu+2n 0'\
\D'l 0 -\\n(0hu-\\n(0du-2n'\
\D'l -\\n(0wu-2n 0'\
\D'l 0 \\n(0hu+\\n(0du+2n'\
'\
\h'\\n(0wu+2n'
. nr 0w +2n
. nr 0d +1n
. nr 0h +1n
..
- space n
- A positive value of the integer n (in hundredths of an em)
sets the vertical spacing before the equation, a negative value sets the
spacing after the equation, replacing the default values. This primitive
provides an interface to groff's \x escape (but with
opposite sign).
- This keyword has no effect if the equation is part of a pic
picture.
- col n { ... }
- ccol n { ... }
- lcol n { ... }
- rcol n { ... }
- pile n { ... }
- cpile n { ... }
- lpile n { ... }
- rpile n { ... }
- The integer value n (in hundredths of an em) increases the
vertical spacing between rows, using groff's \x escape.
Negative values are possible but have no effect. If there is more than a
single value given in a matrix, the biggest one is used.
The appearance of equations is controlled by a large number of parameters. These
can be set using the set command.
- set p n
- This sets parameter p to value n;
n is an integer. For example,
- says that eqn should assume an x height of
0.45 ems.
Possible parameters are as follows. Values are in units of
hundredths of an em unless otherwise stated. These descriptions are intended
to be expository rather than definitive.
- minimum_size
- eqn will not set anything at a smaller point-size than this. The
value is in points.
- fat_offset
- The fat primitive emboldens an equation by overprinting two copies
of the equation horizontally offset by this amount.
- over_hang
- A fraction bar will be longer by twice this amount than the maximum of the
widths of the numerator and denominator; in other words, it will overhang
the numerator and denominator by at least this amount.
- accent_width
- When bar or under is applied to a single character, the line
will be this long. Normally, bar or under produces a line
whose length is the width of the object to which it applies; in the case
of a single character, this tends to produce a line that looks too
long.
- delimiter_factor
- Extensible delimiters produced with the left and right
primitives will have a combined height and depth of at least this many
thousandths of twice the maximum amount by which the sub-equation that the
delimiters enclose extends away from the axis.
- delimiter_shortfall
- Extensible delimiters produced with the left and right
primitives will have a combined height and depth not less than the
difference of twice the maximum amount by which the sub-equation that the
delimiters enclose extends away from the axis and this amount.
- null_delimiter_space
- This much horizontal space is inserted on each side of a fraction.
- script_space
- The width of subscripts and superscripts is increased by this amount.
- thin_space
- This amount of space is automatically inserted after punctuation
characters.
- medium_space
- This amount of space is automatically inserted on either side of binary
operators.
- thick_space
- This amount of space is automatically inserted on either side of
relations.
- x_height
- The height of lowercase letters without ascenders such as `x'.
- axis_height
- The height above the baseline of the center of characters such as `+' and
`−'. It is important that this value is correct for the font you
are using.
- default_rule_thickness
- This should set to the thickness of the \(ru character, or the
thickness of horizontal lines produced with the \D escape
sequence.
- num1
- The over command will shift up the numerator by at least this
amount.
- num2
- The smallover command will shift up the numerator by at least this
amount.
- denom1
- The over command will shift down the denominator by at least this
amount.
- denom2
- The smallover command will shift down the denominator by at least
this amount.
- sup1
- Normally superscripts will be shifted up by at least this amount.
- sup2
- Superscripts within superscripts or upper limits or numerators of
smallover fractions will be shifted up by at least this amount.
This is usually less than sup1.
- sup3
- Superscripts within denominators or square roots or subscripts or lower
limits will be shifted up by at least this amount. This is usually less
than sup2.
- sub1
- Subscripts will normally be shifted down by at least this amount.
- sub2
- When there is both a subscript and a superscript, the subscript will be
shifted down by at least this amount.
- sup_drop
- The baseline of a superscript will be no more than this much amount below
the top of the object on which the superscript is set.
- sub_drop
- The baseline of a subscript will be at least this much below the bottom of
the object on which the subscript is set.
- big_op_spacing1
- The baseline of an upper limit will be at least this much above the top of
the object on which the limit is set.
- big_op_spacing2
- The baseline of a lower limit will be at least this much below the bottom
of the object on which the limit is set.
- big_op_spacing3
- The bottom of an upper limit will be at least this much above the top of
the object on which the limit is set.
- big_op_spacing4
- The top of a lower limit will be at least this much below the bottom of
the object on which the limit is set.
- big_op_spacing5
- This much vertical space will be added above and below limits.
- baseline_sep
- The baselines of the rows in a pile or matrix will normally be this far
apart. In most cases this should be equal to the sum of num1 and
denom1.
- shift_down
- The midpoint between the top baseline and the bottom baseline in a matrix
or pile will be shifted down by this much from the axis. In most cases
this should be equal to axis_height.
- column_sep
- This much space will be added between columns in a matrix.
- matrix_side_sep
- This much space will be added at each side of a matrix.
- draw_lines
- If this is non-zero, lines will be drawn using the \D escape
sequence, rather than with the \l escape sequence and the
\(ru character.
- body_height
- The amount by which the height of the equation exceeds this will be added
as extra space before the line containing the equation (using \x).
The default value is 85.
- body_depth
- The amount by which the depth of the equation exceeds this will be added
as extra space after the line containing the equation (using \x).
The default value is 35.
- nroff
- If this is non-zero, then ndefine will behave like define
and tdefine will be ignored, otherwise tdefine will behave
like define and ndefine will be ignored. The default value
is 0 (This is typically changed to 1 by the eqnrc
file for the ascii, latin1, utf8, and cp1047
devices.)
A more precise description of the role of many of these parameters
can be found in Appendix H of The TeXbook.
Macros can take arguments. In a macro body, $n where n is
between 1 and 9, will be replaced by the n-th argument if the
macro is called with arguments; if there are fewer than
n arguments, it will be replaced by nothing. A word containing a
left parenthesis where the part of the word before the left parenthesis has
been defined using the define command will be recognized as a macro
call with arguments; characters following the left parenthesis up to a
matching right parenthesis will be treated as comma-separated arguments;
commas inside nested parentheses do not terminate an argument.
- sdefine name X anything X
- This is like the define command, but name will not be
recognized if called with arguments.
- include "file"
- copy "file"
- Include the contents of file (include and copy are
synonyms). Lines of file beginning with .EQ or .EN
will be ignored.
- ifdef name X anything X
- If name has been defined by define (or has been
automatically defined because name is the output device) process
anything; otherwise ignore anything. X can be any
character not appearing in anything.
- undef name
- Remove definition of name, making it undefined.
Besides the macros mentioned above, the following definitions are
available: Alpha, Beta, ..., Omega (this is the same as
ALPHA, BETA, ..., OMEGA), ldots (three dots on
the base line), and dollar.
eqn normally uses at least two fonts to set an equation: an italic font
for letters, and a roman font for everything else. The existing gfont
command changes the font that is used as the italic font. By default this
is I. The font that is used as the roman font can be changed
using the new grfont command.
- grfont f
- Set the roman font to f.
The italic primitive uses the current italic font set by
gfont; the roman primitive uses the current roman font set by
grfont. There is also a new gbfont command, which changes the
font used by the bold primitive. If you only use the roman,
italic and bold primitives to changes fonts within an
equation, you can change all the fonts used by your equations just by using
gfont, grfont and gbfont commands.
You can control which characters are treated as letters (and
therefore set in italics) by using the chartype command described
above. A type of letter will cause a character to be set in italic
type. A type of digit will cause a character to be set in roman
type.
- /usr/share/tmac/eqnrc
- Initialization file.
Inline equations will be set at the point size that is current at the beginning
of the input line.
groff(1), troff(1), pic(1), groff_font(5),
The TeXbook